Interesting. The MicroDexed-Touch people have been having problems with recent Teensys not powering on properly. It’s supposedly due to a temporary change in the on board PSU components of recent Teensys.
These are not recent Teensy, I’ve had these a while and it has worked in other projects before I reused it. It’s only certain combinations of supply that cause me problems and in particular with these meanwell IRM10-05, any other supplies I use are ok.
Backplane wiring completed today so testing all 16 voices. I found a few minor faults in my wiring, a bad ground on voice card 5 causing the triangle to be dirty, a pair of gate signals swapped on gates 7&8 of the lower DCO card, a few missing wires from mods that I had made and not fully documented and 3 wires out of sequence on the second DEMUX card causing sub and triangle volume issues, and one voice card is slightly brighter than the others, card 6 voice 1 the filter seems more open. Other than that it’s all working great and now it’s a matter of software and MIDI, let the fun begin. The wiring is the old backplane which I only completed half of before deciding on a new layout.
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First fully polyphonic testing
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Did some work on the bi-timbral functions of the synth, it now plays two sounds at once. A bit weird with some aftertouch thrown in, not intentional but I had just coded that up.
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staggering progress!
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It’s all I have to do in-between the air raid sirens…
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I removed a couple of unused pots and added 3 push buttons for Whole/dual/split modes of the synth. Now it handles incoming midi and routes it accordingly to the upper and lower parts of the synth. Whole mode was the trickiest as I wanted 16 note polyphony, I took my 6 note MIDI to CV converter note assigner and expanded it to 16 notes and it now sends alternate note to channel 1 and 2 to access the upper and lower 8 voices.
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Friday update, I’ve spent a lot of the past week under the weather with flu or something similar. So not a great deal of progress, but I did take this time to investigate the demux side of my design and using a couple of Teensy based testbeds I managed to improve the output of the demux and sample and hold circuits to a satisfying level.
Other improvements have been syncing the LFOs in whole mode so the sound is affected the same across upper and lower synths, this meant dismantling the synth and adding extra wires and a chip for the LFOs to be synced. LFO LEDs now flash in sync when in whole mode. This also brought up a firmware bug in the TAPLFO3C chips which makes the clock out of the slave LED skip when in sync mode. Fortunately Tom had supplied new firmware in the D versions of the chips so when these were installed the skip disappeared.
Also I removed the balance control and repurposed it for a VCA modulation control, not many synths can do this from my experience so I decided it was more useful as I had upper and lower volume control already the balance was redundant. I had a spare VCA and opamp on each demux board to implement this and two spare VCAs around the final output section to modulate the amplitude.
I also fixed the EnvGen looping buttons from on/off to Gated looping, LFO looping and off from a single button and a bi colour led to indicate the state of the looping functions.
Still a lot of work to do software wise on the display when changing it from a single synth to a bi-timbral, but that’s all cosmetic. I also need to cut out a front and rear panel and fit the controls. But I think that’s last in case I make any more changes.
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So about 6 months ago I said I would try and build a bi-timbral synth. Here it is, 16 voice polyphonic, 32 DCOs in all, 4 LFOs, 2 noise sources and two stereo chorus cards. And now the hardware is complete, not the best front panel I’ve ever made and ther are some mistakes on it, but for now it’s ready for some more software updates and testing.
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it’s got a bit of an inverse look to the PE one sam just collected, even the display mirrors the meter on the vintage one.
I love a PB86 push switch too 
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Thanks, some of the sounds
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My hat is off to you Craig. It sounds amazing.
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